duete; see due, ty 2 ]. syn: duty, obligation refer to something a person feels bound to do. A duty often applies to what a person performs in fulfillment of the permanent dictates of conscience, piety, right, or law: one's duty to tell the truth; a parent's duty to raise children properly.
Mutations in the RB1 gene are responsible for most cases of retinoblastoma. RB1 is a tumor suppressor gene, which means that it normally regulates cell growth and keeps cells from dividing too rapidly or in an uncontrolled way.
There are two forms causing achromatopsia: 1  Congenital â this form of cause of achromatopsia is defined as due to malfunction of the retinal phototransduction pathway.  Acquired â this form is due to damage to the thalamus of the mid brain or the cerebral cortex of the brain.